Abstract
The rotational state and ortho-para conversion of on a Pd(210) surface is investigated with rotational-state-selective temperature-programmed desorption (RS-TPD) and theoretical calculations. The isotope dependence of TPD shows a higher desorption energy for than that for , which is ascribed to the rotational and zero-point vibrational energies. The RS-TPD data show that the desorption energy of () (: rotational quantum number) is higher than that of (). This is due to the orientationally anisotropic potential confining the adsorbed , which is in agreement with theoretical calculations. Furthermore, the desorption intensity ratio in and indicates fast ortho-para conversion in the adsorption state, which we estimate to be of the order of 1 s.
- Received 18 October 2017
- Revised 27 December 2017
DOI:https://doi.org/10.1103/PhysRevB.97.085436
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